Norad exercise just prior to Airplanes as weapons

Amalgam Virgo was a multiagency, bilateral air security exercise sponsored by the North American Aerospace Defense Command (NORAD)

The one in this pdf report happend just prior to 9/11 in the summer of 2001. They didn't know about the attack? So they say.

http://www.defenselink.mil/news/Jun2002/n06042002_200206043.html

NORAD-Sponsored Exercise Prepares For Worst-Case Scenarios

This year's exercise is a commercial airliner-hijacking scenario -- planned before the Sept. 11 attacks, Snyder said. Last year's exercise, he said, was a scenario involving a cruise missile launched by "a rogue (government) or somebody" from a barge off the East Coast.